It's an Unreal 3 engine game, so it's likely that tweak guides for UT3 will work for this game as well. The texture problem is something that is an issue with the engine. Changing settings won't likely make any difference.

I usuyaly fint the manual settings myself but Ive searched all the game folders and the folders in My documents but I cant find where to manually edit the settings. I love the game but the Low quality textures is bad.